An internal combustion engine is a power machine which is a heat engine that combusts fuel inside the machine and directly converts heat energy released by the machine into power. A generalized internal combustion engine includes a reciprocating piston type internal combustion engine, a rotary piston engine and a free piston engine and further includes a rotary impeller type gas turbine, a jet engine and the like, while a commonly referred internal combustion engine refers to a piston type internal combustion engine. The most common type of the piston type internal combustion engine is the reciprocating piston type internal combustion engine. A principle of the piston type internal combustion engine is that fuel and air are mixed and combusted in a cylinder, and high-temperature high-pressure gases are produced in the cylinder by the released heat energy. The gases expand to push the piston to work, and mechanical work is outputted through a crank-link mechanism or other mechanisms to drive a driven machine to work. For common diesel engines and gasoline engines, internal energy is converted into mechanical energy, and the internal energy is changed by applying work.